Anatomical knee



d; s. Jbl-INQN' 'May '1;9, 1953 ANAToMIcAL KNEE v 4 sheets-snaai 1- Original Filed July a.. 194s I IN V EN TOR.

May 19, 41953 JOHNSON 2,638,605

ANAToMIcAL KNEE May 19, 1953* original 'Filed July' 3 194s OPV/N JOHNSN INVENToR.

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Patented May 19, 1953 ANATOMICAL KNEE Orvin S. Johnson, El Segundo, Calif., assigner to Northrop Aircraft, Inc., Hawthorne, Calif., a corporation of California Original application July 3, 1948, Serial No. 36,957. Divided and this application April 23, 1951, Serial No. 222,508

. 6 Claims. l

The present invention relates to artiiiciallegs for above-knee amputations, and ,is a division of my copending application, Serial No. 36,957, filed July 3, 1948, entitled Anatomical Knee and Hydraulic Snubber.

The aforesaid pending application concerns itself primarily with the hydraulic snubber arrangement shown herein, whereby a cushioned braking action is applied on the knee mechanism to check or slightly retard the free forward swinging movement ofthe lower leg with respect to the upper leg during the walking cycle, so as to simulate the forward swinging rate of the natural leg. The present invention, on the other hand, is directed tothe linkage arrangement of the knee, and its primary object is to provide an artificial leg that duplicates the action of the natural leg in a more nearly exact manner than has heretofore been possible. f

Locomotion studies of human gaits have established the fact that during each complete walking cycle, the natural knee locks in two separate positions; the rst being when the heel strikes the ground at the forward end of the leg swing, and the second being at the rear end of the leg swing, when the weight is momentarily supported on the toes during the push-off phase. Between the rst and second locked positions,

or while the body is supported on the leg, the 4knee unlocks and flexes slightly to cushion the shock of impact. A further object of the invention, therefore, is to duplicate this sequence of action, and to provide a mechanism that exerts a cushioned braking action on the knee, tending to lock the same'A when the heel strikes the ground, and again during the push-ofi' phase when the weight is carried on the toes.

Another object of the present invention is to provide an artificial leg having a new and improved knee joint mechanism that reproduces almost exactly the geometry of the natural knee. Prior knee joints have, for the most, employ-ed simple hinge pivots; but these fail to duplicate the normal knee action because of the fact that the natural knee joint is not a true hinge. Instead, the shape of the femoral condyles, and the nature of their attachment to the tibial condyles are such that the tibia glides posteriorly on the condyles as the knee is iiexed, producing a combination of rolling and sliding movements. -Such a motion obviously could not take place about one iixed center, and an analysis of the geometry involved reveals the fact that the condyles of the tibia 'glide along a curved path approximating the contour .of the femoral condyles, while the rate of angular displacement of the tibia with respect to the femur varies with the position of the tibial condyles relative to the femoral condyles. As

.the tibial condyles approach the upper rear end of .their curved path, their rate of travel along that path slows down, while the rate of angular displacement of the tibia accelerates.

During exion and extension of the knee, the length of the natural leg changes slightly as a result of the relative sliding movement between the tibial and femoral condyles, and this changing length enters into the pattern of muscular activity and bodily coordination during the walking cycle to produce the smooth, rhythmic motion characteristic of the normal gait. When a single pivot is used at the knee, the leg remains at a constant length for all positions of flexion and extension, .and the amputee finds that the foot tends'to strike the ground during the swinging phase of the walking cycle, unless compensated for by rolling the hips or by raising slightly on the toes of the other foot. The result of such compensatory movement is a limping gait. The improved kneejoint mechanism of the present invention reproduces in the artificial leg the same lengthening and shortening action which takes place in the natural leg, making it possible for the amputee to walk with a symmetrical and natural gait.

Another object of the invention is to provide an artificial leg embodying the features described above, which is, at the same time, extremely simple in construction,` smooth and silent in operation, and free from trouble. f'

The foregoing and other objects and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the preferred embodiment thereof, reference being had to the accompanying drawings, Where- Figure 1 is a perspective view of an artificial leg embodying the principles of the invention;

Figure 2 is a partially cutaway side elevational view of the same;

Figure 3 is a front elevation of the leg;

Figure 4 is a sectional view through the ankle and foot, showing the manner in which the hydraulic snubber control mechanism is actuated by upward deection of vthe toe portion under load; f

Figure 5 is a view similar to Figure 4, but showing the manner in which the control mech- 8-8 in Figure '7;' l

Figure 9 is a side elevational view of their-nee mechanism bent to approximately 90;

Figure 10 is a schematic diagram, .showing fthe manner in which the geometry of the natural knee was derived;

Figure 1l is a side elevational view of vanother form of the invention embodyinga .sing-1:2 fpizvot knee mechanism with a hydraulic snubber for checking the forward swinging movement of the lower leg with respect to the upper; and

Figure l2 is a front .elevational view of the same.

Before 'launching into :the detailed description `of the construction and operation of the prefer-red .embodiment of my invention, it might be -well to describe briefly .the preliminary steps which `were I.necessary in yorder .to derive the geometry ori the natural linee in flexion', so that the action might be accurately duplicated in the mechanical knee.

The iirst step of' the Vpreliminary investigation rwas .to take a series ,of X-.ray pictures oi the natural knee in .progressive .stages .of ilexion, :usi-ng 10,@ .increments from the extended-leg position yof 2'y 'hypereextension to the full-y flexed position .ozf .approximately 135. .oi the femur and tibia were then taken from these X'fray pictures, and the traoings `used .as tem-plates to makeup .plastic models of the bones and :their condyles. These models were then placed .on drawing .paper in the .exact relative positions `occupied .by the bones in .the series of Xeray pictures, .and a composite :dra-wing was made, .comprising Ia series of superimposed outlines which Vwere :drawn .aroundv the models; lkeeping the femur in a single fixed position, and changing the position and angularity oi the tibia. The outlines and relative positions of the femoral vand tibial .condyles for the fully .extended leg .condition are shown in broken lines at and T, respectively, in Figure 1G. t will abe noted that the .tibial 'cond-yle. 'has an upwardly curved load-.bearing surface, which is separated from .the femoral .condyle by an appreciable distance. This .space is. occupied, in the normal knee, by elastic .cartilage which. provides a vcushion ibetween the condyles.

'Tn .order to. nd .the centrode of the tibia, which might be .deined as the .path ,ci the instantaneous center of pure rotation oi the tibia .as it moves. with respect to .the femur, it was deemed .desirable .to treat the problem in terms -ot' the lead center, inasmuch as. the. knee mechanism is essentially a load carrying joint. The load .center was assumed to be at some ,point along a line intersecting the load-.bearing suri lished by, selecting the two points., aoA and bq on the tibial condyles. at` the ends. of. the loadbearing surface. These points were connected by a Vellum tracings line, and the perpendicular bisector cu of that line was then constructed. The line ce represents the load center line of the tibia for the position of the condyles shown in Figure l0. Points al to ag and b1 to b9 were then plotted for nine Jeliierent positions of '.thetibia, 'following which, "corresponding pairs of points were connected,

and perpendicular bisectors e1 to o9 were erected.

It might be well to explain, at this point, that lthe nine positions of the tibia giving the above- Inentioned points in Figure l0 are not spaced vapartan l0". increments, as in the case of the -eray photographs, but are merely nine arbitrarily selected positions lying on the pattern obtained from the Xfray pictures.

g The points of intersection of each of the lines with itscorresponding line a-b, were then connected .by a smooth curve C, which might be termed'the centrode curve of the load center for the tibial condyle. The centrode, itself, is

iound 'by :plotting the points d1 to da formed by the intersection of each of the lines o with the preceding line .c. Thus, pointrdi represents the intersection of line ci with line co; while dz designates the intersection of c2 with ci, and so on. The generally triangular gure D in Figure 10 is the centrode of the tibia, and clearly illustrates eccentric displacement of the instantaneous center of rotation of the tibia which takes place during fie-Xion of the knee.

Since the center of load line for .the tibia glides posteriorly along the oentrode curve C, it became evident, from the start, that the pivot axis of a mechanical knee would have to follow the sam-e curved path C, and that the angular position of the 'lower leg component about the said pivot axis would have to. follow the same curved path C, and that the angular position of the lower leg component about the said pivot axis would have to be controlled in some manner as a function of the linear position oi the pivot axis along the. curve.

inasmuch as the curve `C is non-circular, it was deemed that the pivot axis'oould best be heid to :that path "by a'system of interconnected linliage operating from two fore and' ait spaced points .on the upper leg component, and that the angularityofthe lower leg component might be ,controlled by a link yconnected into the firstnamed linkage.

It was from the foregoingderiva'tion and analysis. of the geometry of the natural'knee that the anatomical knee of thev present invention was developed.

`'The principles of my invention will best be understood byv referring now to Figures l to 9, inclusive, wherein the artificial leg representing the preterrr-:dv embodiment of the invention is design-ated in its entirety by the reference -numeralf, and is seen to comprise upper and lower leg components 2| and 22, respectively, which arerconnected together.'l by a knee joint 23 for relative swinging movement. Mounted on the bottom end of the lower leg component 2:2 is a foot 2d: havingv a hinged toe portion 2li. The upper leg component 2l may-take any desired torrn, and in the present instance comprises a suction socket 26 ot the type which is adapted to be held on the stumpby a slight suction pressure within the Socket.

Attached; to the bottom of the suction socket 25; and; preferably adjustable angularly with respoot theretotabout a vertical aXis, is a base memleer t haying laterally spaced side flanges 'dgl and .3 1 extending downwardly fro-rn opposite sides thereof. A third flange 33 extends downwardly from the bottom of the member 3u pere11e1 to and spaced a short distance laterally from the flange 3 I the two flanges 33 and 3| being drilled to -receive a transversely disposed front pivot shaft 34, and the flanges 32 and 3| being drilled to receive a rear pivot shaft 35 which is parallel to the front pivot shaft and spaced rearwardly from and slightly above the latter. The pivots 34 and 35 are the two fore and aft spaced points about which the knee linkage operates to move the lower leg pivot axis along a path corresponding to the centrode curve C of Figure 10.

The lower leg pivot axis, referred to in the claims as the third pivot, is designated in the drawings bythe reference numeral 36. As best shown in Figure 8, the pivot axis 36 extends coaxially through the cylindrical chamber 31 and operating shaft 38 of a hydraulic snubber 40. The hydraulic snubber 40 constitutes the subject matter of my pending application, Serial No.

36,957, and is fully claimed therein. The following description, therefore, is merely for the purpose of explaining the snubber device illustrated in the drawings so that the mechanism of the artificial leg will be clearly comprehended in its entirety, although it will be understood that the hydraulic snubber forms no part of the present invention. The hydraulic snubber 40 comprises a housing 4| which is xedly mounted on the top end of a tube 42 forming the shank of the lower leg component 22. is preferably, although not necessarily, of the pylon type shown in the drawings, but might take any other desired form. In the case of the pylon construction shown herein, the tube 42, knee 23, and ankle 43 may be enclosed by a cosmetic shell for the sake of limproved appearance and to protect the clothes.

Projecting laterally from one end of the housing 4| coaxial with the pivot axis 36 is a stud 44 that forms the pivot connection for one of the links 45 in the knee mechanism; said link being journaled on a bushing 46 which is pressed onto the stud. At the opposite end of the housing 4| and also coaxial with the pivot axis 36 is another stud 41 which projects from the outer face of a g cover plate member 58. Stud 41 forms the pivot connection for another link 5| in the knee mech- 'anism, and to this end is provided with a bushing 52; The member 5|) is attached to the outer end of housing 4| by a plurality of bolts, and has a cylindrical portion 53 (see Figure 8) projecting into the cylindrical chamber 31. A circumferential groove 54 is cut into the periphery of the cylindrical portion 53, and a rubber O-ring 55 is seated Within the groove to seal the clearances 64 is seated within a groove 65 in the end of shaft 38 to hold the link 63 in place. An annular channel 66 is formed in the surface of the bore 56, and seated therein is an O-ring 61 which seals the clearances between the shaft 38 and bore 56. v

Formed integrally with the member 50 and .projecting laterally therefrom to the inner end of the chamber 31 is a wedge-shaped partition member 10 which is shaped to fill the'space'be- The lower leg component 22 y pivot 35.

tween the wall of chamber 31 and the peripheral surface of shaft 38. A cylindrical valve chamber 1| extends into the' partition 10 from the inner end thereof, and rotatable Within this chamber is a valve plug 12 having a generally cone-shaped port 13' provided therein, the purpose of which will become apparent presently. The valve plug 12 has a stem 14'projecting axially therefrom through an opening in the housing 4|, and mounted on the outer end of the stem is an operating arm 15. An O-ring 16 seals the stem. 14 against leakage.

Two passageways and 8| are drilled into the valve chamber 1| from opposite sides of the par- .tition 10, and these passageways cooperate with the valve port 13 to provide restricted communication between the two sides of the partition. The cylindrical chamber 31 is filled with hydraulic fluid, which is forced through the passageways in the partition 10 by a vane 82 on the shaft 36. The vane 82 is keyed into the shaft 38 and cooperates with the partition member 16 to divide the chamber 31 into two compartments. As the Vane 82 rotates with the shaft 38, fluid is forced from one of the compartments through the passages 80, 8|, and valve port 13 into the other compartment. As shown in Figure 7, the valve plug 12 is normally positioned so that the port 'I3 is fully registered with passageways 8|] and 8|. When the Valve plug 12 is rotated in a clockwise direction, the small end of the valve port 13 passes beyond the opening of passageway 8|),

'and the walls of chamber 31 against leakage.

The construction and arrangement of the link- 4age in the knee mechanism 23 will best be understood by referring now to Figures 2 and 3, wherein it will be seen that link 63 is connected at its top end by a pivot bolt 86 to one arm 81 of the bell crank 66. The bell crank 88 is journaled on the front pivot shaft 34 between supporting flanges 3| and 33, and has a second arm 89 spaced 180 from arm81. Arm 81 extends downwardly and rearwardly from pivot 34, while `arm 89 extends upwardly and forwardly therefrom, and is connected by a pivot bolt 96 to the front end of a link 9|. The rear end of link 9| is connected by a pivot bolt 92 to an arm 93 of a bell crank 94 which is journaled on the rear Another arm 95 ofthe bell crank 94 extends downwardly and forwardly yfrom the pivot 35 and is connected by a pivot bolt 96 to the top end of link 45.

It will be noted in Figure 3 that the hub of bell crank 94 is quite elongated and extends across the width of the base member 30 from flange 3| tolflange 32. Arm 93 is at the left hand end of the bell crank 94, while arm 95 is at the right hand end thereof. Another arm 91 (see Figure 1) extends downwardly and forwardly from the bell crank 94 parallel to arm 95 and of the same length as the latter, but at the same end of the bell crank as arm 93. Arm 91 is connected by a pivot bolt 98 to link 5| which is parallel and equal and the two laterally spaced approximately 3% arms 95e, 9T, and. links 4,5', 5,1, provide lateral rigidity in the knee structure.

Another arm 99 extends downwardly and rearwardly from the bell crank S4 adjacent the arm and this last-named arm is connected by a pivot bolt Hi8. to a forwardly extending link IDI. The front end of the link 10| is connected by a pivot bolt |62 to an arm |83, which is fkcrined integrally with the housing 4l and extends upwardly and forwardly therefrom.

The linkage system formed by links 45. 5l, B3 and 9| and by bell cranks 823 and 9,4 serves to control the travel of the bottom pivot 3 6 to a curved path substantially identical to the centrode curve C shown in Figure l0, while bell crank arm 53 and link [0| serve to stabilize the lower ieg about the bottom pivot 36 and to control the angularity of the lower leg to the flexion pattern indicated by the lines cil-cg. The particular geometric patterns of Figure 10 are obtained in the mechanical knee 23 by virtue of certain angular relationships and proportional lengths which will now be described.

Reference is had now to Figure 2, which shows the knee 23 in the extended-leg position. In this condition, link 63 is disposed at an angle of approximately 135 to bell crank arm t'i, while the other bell crank arm 86 is disposed at an angle of approximately 62 to link 9i. Each of these angular relationships is measured as the included angle between intersecting lines drawn through the centers of the pivot connections at the ends or" the members involved. Link 9i is at approximately 92 to bell crank arm 5st, while the latter is approximately 135 to bell crank arms 95 and 9i, respectively. Bell crank arm 99 is approximately 58 to bell crank arin 95, or 167 to arm 93. Link lill is at approximately 62 to arm 99, and approximately 74V2 to a line drawn through .the center of pivot bolt |62 and bottom pivot 36.

One other angle which enters into the picture is the inciuded angle between the axes. of pivots 3,4, 36 and 35; the said angle being approximately 28.

The proportional lengths of the several parts are best disclosed by giving the actual dimensions,

vin inches, of a typical knee designed for a man of average height'and bone structure. The center-to-center distance from pivot axis 335` to pivot bolt St (i. e., the effective length of link 63) is The center-to-center distance from pivot bolt @t to pivot gli, and from 34 to pivot bolt 9e is i and respectively. The distance from the center o f pivot bolt 9i? to pivot bolt 92 (the effective length of link 9i) is approximately 21/2". The distance from the center o f pivot bolt 92 to the axis of pivot 35 is approximately l-lfi, while the distance from the axis of pivot 35 to the center or pivot bolt 96 is approximately 11/4. The distance from the center of pivot 96 to pivot axis 36 (i. e., the effective length of link .45) and .trom pivot bolt 68 to pivot axis 35 (the effective length Q link 5l) is approximately 3%" each. The distance from ,the axis of pivot ,35 to the center of pivot bolt 4H1!) (bell crank arm es) is approximately 23j5; from the center of pivot-bolt it@ to the center .of pivot holt i62 is approximately is/8; and from the center of pivot bolt 162 to the pivot axis 3.6 is approximately 2%. It should be understood that the actual dimensions 4given above are not, in themselves,Y signicant, but rather, it is the proportional lengths .of the several members with respect to .theo-.thers that is critical. In the case ,of a mall ,of shorter than average height, the correct knee action would be obtained by reducing 8 allv of the dimensions by the same proportional amount; while the reverse procedure would be followed. the oase of. a. man of greater than average height. The angular relationship between the several parts, would, ofcourse, rernain the same fior all, sizes of the knee mechanism.

It might be noted at this point that when the leg is fully extended, as in Figure 2,V the axis 36 of the hinge pivot is located posterior to the vertical. line of the center of gravity of the body, causing the pivot to go past the centerline as the leg is extended, giving about two degrees of hyperextension, which gives stability to the joint. The knee joint is stopped at this 2 of hyper-extension by means of alirnit stop. bracket m5' which straddles the front edges of flanges ill and 33V. A strip I i or composition material is attached to the inside face oi the bracket 1.65 and serves as a bumper for the bell crank arm 8 3 to limit the counterclockwise rotation ofy the latter.

When the knee is flexed, the rearward swinging movement of the lower leg 2l about the pivot axis 36 causes the arm i653 to swing downwardly and forwardly in a counterclockwise direction (Figure 2), pulling the link lill forwardly and rocking bell crank Sil in a clockwise direction. Bell crank fili,` acting through link 6i, rocks. the bell crank 8 8A in a clockwise direction. As the pivot 35 moves downwardly and forwardly with clockwise rotation of bell crank 88, the distance between front pivot 3i and bottom pivot 36 increases at a diminishing rate of change, while the distance from pivot axis 36., to rear pivot 35 decreases at an increasing rate Of Change. This condition continues until, the lower leg compo.- nent 22 reaches an angle of about 50 to the upper leg component, at which point the pivot bolt 86 passes dead center between pivots 34,V and 36. From that point on, the distance from pivot 33.0. to pivot axis 35 decreases at an increasing rate ofY change, while the distance between rear pivots 35 and bottom pivot 36 continues to diminish at an accelerated rate of change.

One important detail in the proper function.- ing ofA the leg has to d o with the application of a cushioned' braking` action on the knee 23 responsive to plantar nexion of the foot '24 or to upward deiiection of the. hinged toe portion 25,. This braking action gives the same sequence of locking 'and unlocking at the knee which is obtainedA in the natural leg during the Walking cycle, and also enables the ainputee tov recover from a fall by restraining the flexion of theknee tp a slow, controlled rate when the weight` is thrown suddenly on either the heel or toe portion.` Still another advantageous feature of the above-mentioned locking action is that it enables the amputee tol walk down an inclined surface without having the knee vfold up beneath him.

IA-he braking Iaction referred to above lis obtained by controlling the valve 'i2` in the hydraulic snubber Mi with linkage means actuated by the foot 24 and hinged toe portion 275. To this end, the operating lever l5 of the valve 7,2 is connected by a link Hi) to a lever arm HI which is pivoted at H2 on the snubber housing 44. A push-rod H3 is connected at H4 to the 'arri-1` il! and extends downwardly therefrom through the center ofthe hollow tube 42. The bottom end of the push rod extends through and is slidable within a guide bushing I t5 which is pressed' into a hole in a circular plate H6' at the bottom end of the tube i121;4 said plate being: held in placeby a cap, member i-ZU- which is riveted` or otherwise suitably xed to the bottom end of the tube `42.

, The cap member |20 has. a pair of laterally spaced ears |2 I `on the bottom end thereof which are 'drilled and bushed to provide a.- journal for a transverse tubular shaft I 22, forming the hinge pivot for the ankle 43. The ends of the tubular shaft |22 project beyond the ears |2| and are fixedly received within holes in the ends of arms |23 of -a saddle member |24. A threaded stud |25 extends downwardly from the bight portion of the saddle |24 through a hole in the foot 24, and is secured by a nut |26.

Projecting forwardly from the front of the cap member |20 lat the lower end thereof `is a horizontal shelf |30, which is engageable with the top end of a rubber instep bumper |32 that is set into a recess in the top surface of the foot. An upwardly inclined rear shelf |3| projects from the back of member |20 vand is engageable with the top end of a rubber heel cushion 33. The two cushions |32 and |33 engage their respective shelves to locate the foot in its normal position, as shown in Figure 2. The instep cushion 32, being rather short, permits only a very limited amount of d'orsiflexion lof the foot, While the heel cushion |33, being quite long 'and resilient, permits a greater Adegree of plantar flexion. f

The toe portion 25 is connected to the foot 24` by a transverse hinge |35 which permits the toe to deflect upwardly with respect to the foot. The toe portion 25 is yieldingly held in the extended position shown in Figure 2 by a rubber cushion |36 which is compressed, as shown in Figure 4, when the toe portion is deflected upwardly. Mounted on the lback side of the toe portion 25 is a bracket |40 that is connected by a pin |4| to the front end of a turnbuckle link |42; the rear end of said link being connected by a pin |43 to an arm |44 extending down- -wardly from `a cam |45. The cam |45 is Ijournaled on the ankle pivot shaft |22 .betweenA the ears |2|, and is provided wtha lobe |46 which is normally positioned asshown in Figure 2. Bearing downwardly on the peripheral edge of the cam |45 from above is a cam follower, preferably in the form of a roller |50 which is yconfined within a U-shaped recess in the bottom of a guide member |52. The yguide member |52 is screwed onto the bottom end ofpush rod ||3, and is provided on its front and rear sides with flanges portions which vslide up and down in vertical ways |53' in the cap member |20. The roller |50 is held vdownwardly against the periphery of the cam |45 -by a compression spring |54 which encircles the push rod ||3 vand bears downwardly against a spring keeper |55. The roller |50 is confined against axial displacement from the recess |5| by the side walls |56 (see Figure 6) of thecap member |20, which lie closely adjacent the ends of the roller.

When'the hinged toe portion 25 is deected upwardly with respect to the foot, as shownin Figure 4, the turnbuckle link |42 is pushed rearwardly, rocking the cam |45 in a countercl-ockance to rotation of the vane 82 and thereby restraining the knee against further flexion. When the weight is removed from the toe portion 25, the resiliency of rubber cushion |36 causes the toe portion to be returned to its initial position, thereby restoring the cam member |45 to the position shown in Figure 2; while the spring |54 urges the push rod I3 downwardly to reopen the valve member 12.

The hydraulic snubber valve 12 is also moved toward the closed position when the foot 24 is deflected to the position of plantar flexion shown in Figure 5. vThis is the condition which is obtained when the weight is thrown on the heel at the end of the forward swing phase of the leg during thewalking cycle. The resistance of the rubber cushion 36 to compression causes the toe portion to be held in its normal position, with theresult that the turnbuckle link |42y andcamr |45 remain lstationary with respect to the foot while the latter is rocked about the `ankle pivot |22. As the cam rotates with the foot, the lobe |45 raises the roller |50 and pushes the rod 3 upwardly against the pressure of spring |54, to rot-atey the valve plug 12 toward the closed position. When the weight is removed from the heel, the resiliency of the compressed heel bumper |33 causes the foot .to be returned to its norm-a1 position, which has the effect of restoring the valve plug 12 to its normal open position.

It is believed that the construction and operation of the knee mechanism and hydraulic snubber which are embodied in the preferred form of the invention shown in Figures 1 to 10, inclusive, will be clearly understood from the foregoing description.

Another form of the invention, featuring the hydraulic snubber and brake in a single pivot knee, is shown i'n Figures 11 and 12, to which reference will now be had. In this embodiment, parts having the same functions as those in Figures l to 10 have been given the same reference numerals with the suffix a.

, the top end of the lower leg tube 42a. Ear ISI is drilled to receive the stationary stud 44a at one end of the housing 4|a, vand is rotatable thereon. Ear |00 is drilled coaxial with the hole in the other ear, and receives. the serrated, projecting end of the operating shaft 38aof the snubber. rIhe operating shaft 38a is thus held stationary with respect to the upper leg component 2|a, while the snubber housing 4|a, being rigidly mounted onthe upper end of the lower leg como ponent 22a, rotates with the latter. The mechawise direction. The roller |50 is lifted bythe cam lobe |46, pushing the rod ||3 upwardly and raising the valve operating lever 15, whichcloses the valve port 13 with respect to the passageway 80. Flexion of the knee causes the vane 82 to rotate in a clockwise direction, as seen in Figy ure 7, and this forces hydraulic fluid from the bottom side of the partition 10 to the top side thereof through the passageways 8|, 80, and valve port 13. Partial closing pf the valve member 12 throttles Vthis flow of hydraulic fluid tnrpugnthe partition member, creating `resistn nism in the hydraulic snubber 40a is the same as that shown in Figures 7 and 8, and therefore need not be described in detail again. The control mechanism in the footfor operating the valve of the hydraulic snubber is likewise the same as that shown in Figures 4, 5 and 6, and its operation is also .the same. Thus, the hydraulic snubber and the control mechanism for applying a cushioned braking action on the flexion of the knee is adapted for use in a single pivot knee as well as in an anatomical knee of the type shown in Figures l to 10.v

While I have shown and described in considerable detail whatI believe to be the preferred form of my invention, it is to be understood that such details are not restrictive, and that various changes may be made in the shape and arrangement of the several parts without departing from the broad scope of the invention, as dened in the appended claims.

I claim:

l. In an artiiicial leg having upper and lower leg components, a knee joint connecting said components together for relative swinging movement, comprising a transverse pivot adjacent the upper end of said lower leg component, link means connected to said upper leg component at fore and aft spaced points thereon, said link means being connected to said pivot and being operative to swing the latter rearwardly and upwardly in a curved, non-circular path from an initial extended-leg position, and other link means interconnecting said first-named link means with said lower leg component for swinging the latter about said pivot to a predetermined angular relationship with respect to said upper leg component for any given position of said pivot along said curved path.

2. In an artificial leg having upper and lower leg components, a knee joint connecting said components together for relative swinging movem ment, comprising front and rear pivots on said upper leg component which are spaced apart from one another in a fore and aft direction, a third pivot on said lower leg component spaced downwardly from said front and rear pivots, interconnected link means connecting said third pivot with said front and rear pivots, whereby said third pivot is constrained to move rearwardly and upwardly in a curved, non-circular path from anv initial extended-leg position, and other link means operatively connected into said firstnamed link means and attached to said lower leg component at a point spaced from said third pivot, whereby said lower leg component is maintained at a predetermined angular relationship with respect to said upper leg component for any given position of said third pivot along its curved path.

3. In an artiiicial leg having upper and lower` leg components, a knee joint connecting vsaid components together for relative swinging movement, comprising front and rear pivots on said upper leg component which are spaced apart from one another in a fore and aft direction, a third pivot on said lower leg component spaced downwardly from said front and rear pivots, a bell crank journaled on said front pivot, another bell crank journaled on said rear pivot, a link connecting said third pivot to one arm of said rst named bell crank, another link connecting said third pivot to one arm of said last-named bell. l

crank, another link connecting another arm of said firstmamed bell crank to another arm of said last-named bell crank, said links and bell cranks coacting with one another to constrain the movement of said third pivot to a rearwardly and upwardly curved, non-circular path from an initial extended-leg position, and another link connected to a third arm on one of said bell cranks and to said lower leg component, for maintaining the latter at a predetermined angular relationship with respect to said upper leg component for any given position of said third pivot along its curved path.

4. In an artificial leg having upper and lower leg components, a knee joint connecting said components together for relative swinging movement, comprising front and rear pivots on said upper leg component which are spaced apart from one another in a fore and aft direction, a

third pivot on said lower leg component spaced downwardly from said front and rear pivots, the included angle between said' front pivot, third pivot, and rear pivot being approximately 28, a bell crank journaledon said front pivot and having an arm extending downwardly and rearwardly therefrom, a link connecting said third pivot with said arm, the included angle between said link and said arm being approximately another fbell crank journaled on said rear pivot and having an arm extending downwardlyl and forwardly therefrom, a link connecting said third pivot with said last named arm, the 'included angle between said last-named link and said last-named arm being approximately 168, said first named bell crank having a second arm disposed at tol the first-named arm thereof, said last-named bell crank having a second arm extending upwardly and forwardly from the pivot-axis thereof at an angle of approximately 135 to the rst arm thereof, a link connecting said second arm of said first-named bell crank with said second arm of said last-named bell crank, said links and said bell cranks coacting with one another to constrain the movement of said third pivot to a rearwardly and upwardly curved, non-circular path corresponding to the centrode curve 0f the load center, for the tibial condyles of the natural knee, and another link connecting a third arm on one of said bell cranks with said lower leg component at a point spaced from said third pivot, whereby said lower leg component is maintained at a predetermined angular relationship with respect to said upper leg -component for any givenv position of said third pivot along its curved path.

5.. In an artificial leg having upper and lower leg components, a knee joint connecting said components together for relative swinging movement, comprising front and rear pivots on said upper leg component which are spaced apart from one another in a fore and aft direction, a third pivot on said lower leg component spaced downwardly from said. front and rear pivots, the included angle between said front pivot, third pivot, and rear pivot being approximately 28, a bell crank journaled on said front pivot and having an arm extending downwardly and rearwardly therefrom, a link connecting said third pivot with said arm, the included angle between said link and said arm being approximately 1.35?, another bell crank journaled on said rear pivot and having an arm extending downwardly and forwardly therefrom, a link connecting said third pivot with said last named arm, the included angle between said last-named link and said lastmamed arm being approximately 158, said first-named bell crank having .a second arm disposed at 130 to the iirst-named arm thereof, said last-named bell crank having a secondv arm extending upwardly and forwardly from the pivot-axis thereof at an angle of approximately to the` rst arm thereof, a link connecting said second arm of said nrst-named bell crank with said second arm of said last-named bell crank, said links and said bell cranks coacting withy one another to constrain theI movement of said third pivot to a rearwardly and upwardly curved, non-circular path corresponding to the centrode curve of the load center for the tibial condyles of the natural knee, a third arm extending downwardly and rearwardly from said last-named bell crank at an angle of approximately 58 to the first arm thereof, and a link connecting said third arm with said lower leg componentl at a point spaced upwardly and forwardly from said third pivot, the included angle between said third arm and said last-named link being approximately 62, and the included angle between said last-named link and a line drawn through the pivot axis of its connection to said lower leg component and the center of said third pivot being approximately 74, whereby said lower leg component is constrained to rotate about said third pivot in a manner closely approximating the angular exion pattern of the tibia in the natural leg.

6. In an artificial leg having upper and lower leg components, a knee joint connecting said components together for relative swinging movement, comprising front and rear pivots on said upper leg component which are spaced apart from one another in a fore and aft direction a distance of approximately 21/81, where Z represents a -given unit of length, a third pivot on said lower leg component spaced downwardly from said front and rear pivots, the included angle between said front pivot, third pivot, and rear pivot being approximately 28, a bell crank journaled on said front pivot and having a rst arm extending downwardly and rearwardly therefrom, and a second arm at 180 to said rst arm, a link connecting said third pivot with said first arm, the included angle between said link and said rstarm being aproximately 135, and the center-to-center distance between the pivot connections at the ends of said link being approximately 3%1, another bell crank journaled on said rear pivot and having a rst arm extending downwardly and forwardly therefrom, a second arm extending upwardly and forwardly from said rear pivot at approximately 135 to said first arm, and a third arm disposed at ap#- proximately 167 to said second arm, a link connecting said third pivot with said rst arm on said last-named bell crank, the included angle rbetween said last-named link and said rst arm being approximately 168, and the center-to- -center distance between the pivot connections at the ends of said last-named link being approximately 31M, a link connecting said second arm of said first-named bell crank with said second arm of said last-named bell crank, the center-to-center distance between the pivot connections at the ends of said last-named link being approximately 212l, the distance from the center of said front pivot to the centers of the pivot connections at the ends oi' both the first and second arms of said rst-na1ned bell crank being 1l and 1l, respectively, the distances from the center of said rear pivot to the centers of the pivot connections at the ends of said rst, second, and third arms of` said last-named bell crank being approximately 11/41, 11/4Z, and 21%1, respectively, said links and said bell cranks coacting with one another to constrain the movement of said third pivot to a rearwardly and upwardly curved, non-circular path corresponding to the centrode curve of the load center for the tibial condyles of the natural knee, and another link connecting said third arm on said last-named bell crank with said lower leg component at a point spaced upwardly and forwardly from said third pivot, the included angle between said third arm and said last-named link being approximately 62, and the center-to-center distance between the pivot connections at the ends of said last-named link 'being approximately 3%1, said last-named link being operative to rotate said lower leg component about said third pivot to a predetermined angular position for each position of said third pivot along said curved path, so as to approximate the angular exion pattern of the tibia in the natural leg.

UNITED STATES PATENTS Name Date Greissinger June 30, 1936 Number 

